MySQL删除所有未选中的记录

Question

我正在尝试根据时间戳删除除最近的 25 个条目之外的所有条目。我试过这个:

DELETE FROM `chat` WHERE `IndexNo` NOT IN(SELECT `IndexNo` FROM `chat` ORDER BY `Timestamp` DESC LIMIT 25)

产生这个错误:

#1235 - This version of MySQL doesn't yet support 'LIMIT & IN/ALL/ANY/SOME subquery'

有没有办法做到这一点？

Answer 1

您不能依赖 IN/ALL/ANY/SOME 子查询中的 LIMIT，而是可以使用多删除语法:

DELETE 
  `chat` 
FROM 
  `chat` 
    LEFT JOIN (SELECT `IndexNo` FROM `chat` ORDER BY `Timestamp` DESC LIMIT 25) AS `selected`
      ON `chat`.`IndexNo`=`selected`.`IndexNo` 
WHERE 
  `selected`.`IndexNo` IS NULL;

-根据manual , 这将从 MySQL 5.0 开始起作用